CD8+ T cells specific for antigens expressed only in particular tissues are important in the pathogenesis of organ-specific autoimmune diseases and allograft rejection, but the mechanisms of recruitment of T cells in these settings are poorly understood. There are likely to be unique aspects of recruitment of tissue antigen-specific T cells, due to the abundance of the tissue antigens, the absence of infection, and the particular characteristics of each organ's vascular bed. This project will focus on endothelial-dependent recruitment mechanisms of pathogenic tissue antigen-specific CD8 + T cells. The approach will rely on transgenic mouse models in which well-defined populations of TCR-transgenic T cells specific for a defined antigen are introduced into mice that express transgene-encoded antigen in an organ specific manner. In Specific Aim #1, the role of selectins in tissue antigen-specific CD8* recruitment will be examined. This Aim will test the hypothesis that selectin-dependent adhesion to endothelium is a key step in the recruitment of these CD8* T cells. The studies will examine different subsets of CD8* T cells, and different tissues. The experiments will involve transgenic models of CD8* T cell-mediated autoimmune myocarditis, pancreatic islet inflammation, nephritis, and bronchiolitis. The recruitment and pathogenicity of CD8- T cells with altered selectin-ligand expression will be quantitatively compared with control T cells. Specific Aim #2 will focus on how chemokines influence recruitment of tissue antigen-specific CD8+ T cells. The underlying hypothesis is that chemokines expressed in tissues will differentially effect the recruitment of CD8+ T cells, depending on the vascular bed and the subset-phenotype of the T cells. The emphasis will be on CXCR and CCR5 binding chemokines. The experimental approach will rely on the same transgenic models of autoreactive T cell recruitment used in Aim 1, in combination with pharmacologic chemokine receptor blockade, and chemokine or chemokine receptor gene knock-out mice. In Specific Aim #3, the role of endothelial antigen-presentation in direct T cell recruitment will be studied. The experiments will directly examine antigen-specific interactions of CD8+ T cells and endothelium in vivo, using sensitive techniques including intravital microscopy.